The invention relates generally to medical devices and procedures, and more particularly to medical devices and procedures for preventing bone cement extravasation during surgical procedures.
Bone cement is the term typically used to refer to polymethyl methacrylate (PMMA), which is commonly used to reinforce or augment bone structures. For example, bone screws are often used to stabilize bone structures within the body, such as during a spinal fracture repair procedure. Such bone screws can be implanted into the vertebral pedicle (and are therefore sometimes referred to as pedicle screws) in conjunction with other structural members, such as, for example, rods, bars and/or plates to realign and stabilize a compromised spine.
Unfortunately, after implantation into a host bone structure, bone screws can be susceptible to becoming “pulled out” from the host bone structure, loosened within the host bone structure and/or destabilized within the host bone structure. The susceptibility of a bone screw to pullout, loosening and/or destabilization can be compounded when the bone screw is implanted into soft portions of a bone structure (e.g., cancellous bone or diseased bone) and/or the bone screw is subjected to high loads.
Consequently, bone cement is frequently used to augment the pull-out strength of known bone screws. For example, fenestrated screws have been developed that include a central channel (cannulation) and multiple fenestrations along the shaft. Bone cement injected through the central channel can then be dispersed through the fenestrations into the surrounding bone, thereby providing a reinforced structure that can enable more secure fixation of the screw.
However, the use of bone cement in such procedures introduces additional risks—in particular the risks associated with extravasation of the bone cement from the bone environment. The polymerization of PMMA is an exothermic reaction that can cause necrosis of adjacent cells. In addition, PMMA exhibits toxicity that can cause pulmonary embolism or neurologic deficit if allowed to come into contact with vessels or nerves. This extravasation risk is present in other procedures that make use of bone cement, such as vertebroplasty and kyphoplasty.
Accordingly, it is desirable to provide systems and methods for minimizing the risk of extravasation during surgical procedures involving the use of bone cement.